Charge-controlled polyurethane foam and toner-conveying roller using the same

ABSTRACT

Provided are charge-controlled polyurethane foam by which the influence of electrification by friction between toner on the surface layer of a toner-conveying roller and a developing roller can be sufficiently prevented and by which a good image can be stably obtained with a low cost, and a toner-conveying roller using the same. 
     The charge-controlled polyurethane foam is the one wherein the surface layer of the polyurethane foam is impregnated with a charge control agent which is on the negative side or on the positive side in the triboelectric series with respect to substrate polyurethane foam. The toner-conveying roller is the one which supports the charge-controlled polyurethane foam on the periphery of the axis of the roller.

TECHNICAL FIELD

The present invention relates to charge-controlled polyurethane foam anda toner-conveying roller using the same (hereinafter, also simplyreferred to as “a roller”), and particularly, to charge-controlledpolyurethane foam used for a toner-conveying roller which is used forproviding with toner a developing roller which forms a visible image onthe surface of an image forming body such as a photoconductor or a paperby conveying toner (developer) to the image forming body in an imageforming apparatus such as a copier or a printer, and a toner-conveyingroller using the same.

BACKGROUND ART

In general, in a developing unit of an electrophotography image formingapparatus or the like such as a copier or a printer, as shown in FIG. 3,an image forming body 11 such as a photoconductor retaining anelectrostatic latent image, a developing roller 12 which makes theelectrostatic latent image a visible image by making the image formingbody 11 come in contact with the roller and attaching toner 20 which issupported on the surface of the roller to the image forming body 11, anda toner-conveying roller 13 (including a toner-providing roller and acleaning roller for sweeping off unwanted toner) for providing thedeveloping roller 12 with toner are provided, and an image formation isperformed by a series of processes in which the toner 20 is conveyedfrom a toner storage unit 14, via the toner-conveying roller 13 and thedeveloping roller 12, to the image forming body 11. In this figure, 15represents a transfer roller, 16 a charge unit, 17 an exposure unit, and18 a blade for sweeping off toner.

Among these, the toner-conveying roller 13 is formed in a structure thatan electrically conductive elastic body such as polyurethane foam issupported on the periphery of the axis via an adhesion layer from aviewpoint that the toner-conveying roller 13 should not damage thedeveloping roller 12 by coming in contact with the developing roller 12,and from a viewpoint that a grip performance is ensured by increasingcontact area of the rollers or the like. Examples of functions requiredfor the toner-conveying roller 13 include a toner conveying ability, atoner charging ability, and a toner sweeping ability. In order tosatisfy these functions, various measures have been taken.

For example, by using a method in which electrically conductivetreatment liquid such as electrically conductive carbon black or thelike is impregnated in a polyurethane foam which constitutes thetoner-conveying roller 13 (see, Patent Documents 1 to 3), or by using amethod in which an electrically conductive carbon is kneaded, anelectric resistance is reduced, a toner charge amount (Q/M) isdecreased, and a toner conveying amount (M/A) is heightened, whereby afailure of an image blur during an endurance image evaluation has notbeen allowed to occur.

Without using an electrically conductive material such as carbon, byembossing the surface of the toner-conveying roller 13 to heightenphysically the toner conveying amount (M/A), a failure such as an imageblur during an endurance image evaluation has not been allowed to occur(see, Patent Document 4).

Further, it has been known that the toner conveying ability increases byexposing apart of fine particles for charging toner from an elastomericfoam layer (see Patent Document 5).

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. S57-115433 (Claims and the like)-   Patent Document 2: Japanese Unexamined Patent Application    Publication No. 2002-319315 (Claims and the like)-   Patent Document 3: Japanese Unexamined Patent Application    Publication No. 2003-215905 (Claims and the like)-   Patent Document 4: Japanese Unexamined Patent Application    Publication No. H11-38749 (Claims and the like)-   Patent Document 5: Japanese Unexamined Patent Application    Publication No. 2008-116607 (Claims and the like)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in any of the methods described in Patent Documents 1 to 3,because the polyurethane foam is impregnated with an electricallyconductive material, the influence of electrification by frictionbetween toner on the surface layer of a toner-conveying roller and adeveloping roller cannot be sufficiently prevented, and thus, asufficient toner conveying ability cannot be obtained, thereby togenerate a failure such as an image blur during an endurance imageevaluation.

In the method of kneading carbon in polyurethane foam, although there isno need to worry about an image failure due to the absence of carbondetachment, because carbon is dispersed and molding by a mold is forcedto be performed in the polyurethane foam molding process, a small lotproduction in a batch manner is required, which leads to cost increases.

Further, in the method described in Patent Document 4, a toner-conveyingroller having a high resistance is used without using carbon and aconcavo-convex shape is required to be formed on the surface of theroller, and thus the roller is generally molded in a mold (cavity) whoseinside has a concavo-convex shape. Therefore, there have been variouscost increasing factors following the molding of the respective rollerssuch as a mold cost, a mold maintenance and a mold releasing propertyprocess inside the mold (mold release agent, fluorine coating).

Further, in the method described in Patent Document 5, in which a partof fine particles for charging toner is exposed by simple adhesion ofthe fine particles for charging toner on the surface of the roller, forexample, by spraying an adhesive on the surface of the roller and thenadhering fine particles for charging toner, there are problems in thatthe fine particles for charging toner damage the other members togenerate a poor image, and in that an image density decreases due to adecrease in the charge amount during an endurance.

Accordingly, an object of the present invention is to solve theabove-mentioned problems, and to provide charge-controlled polyurethanefoam by which the influence of electrification by friction between toneron the surface layer of a toner-conveying roller and a developing rollercan be sufficiently prevented and by which a good image can be stablyobtained with a low cost, and a toner-conveying roller using the same.

Means for Solving the Problems

To solve the above-mentioned problems, the present inventors intensivelystudied to discover that the problems can be solved by employingcharge-controlled polyurethane foam which is impregnated with aspecified charge control agent in the surface layer, thereby completingthe present invention.

That is, charge-controlled polyurethane foam of the present invention ischaracterized in that the surface layer of the polyurethane foam isimpregnated with a charge control agent which is on the negative side oron the positive side in the triboelectric series with respect to thesubstrate polyurethane foam.

The charge-controlled polyurethane foam of the present invention ispreferably polyurethane foam wherein said substrate polyurethane foam issubstrate polyurethane foam impregnated with carbon conductive materialor substrate polyurethane foam in which carbon conductive material isadded inside.

A toner-conveying roller of the present invention is characterized bysupporting the charge-controlled polyurethane foam on the periphery ofthe axis of the roller.

The toner-conveying roller of the present invention is preferably aroller wherein said charge control agent is on the negative side in thetriboelectric series with respect to said substrate polyurethane foam,and wherein the roller is for positively charged toner; or is preferablya roller wherein said charge control agent is on the positive side inthe triboelectric series with respect to said substrate polyurethanefoam, and wherein the roller is for negatively charged toner.

Effects of the Invention

According to the present invention, by the above-mentioned constitution,it became possible to attain charge-controlled polyurethane foam bywhich the influence of electrification by friction between toner on thesurface layer of a toner-conveying roller and a developing roller can besufficiently prevented and by which a good image can be stably obtainedwith a low cost, and a toner-conveying roller using the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the toner-conveying roller of oneembodiment of the present invention in the width direction.

FIG. 2 is an illustrative view which illustrates a mechanism in whichtoner is conveyed from a toner-conveying roller to a developing roller.

FIG. 3 is an illustrative schematic view of one example of an imageforming apparatus.

MODES FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described indetail with reference to the figures.

Charge-controlled polyurethane foam of the present invention is the onewherein the surface layer of the polyurethane foam is impregnated with acharge control agent which is on the negative side or on the positiveside in the triboelectric series with respect to the substratepolyurethane foam. By this, the influence of electrification by frictionbetween toner on the surface of a toner-conveying roller and adeveloping roller can be sufficiently prevented. Also, by impregnatingwith the charge control agent, detachment of the charge control agent isprevented, and therefore, the effect of providing charging ability canbe stably generated, whereby a good image can be obtained with a lowcost. As used herein, “surface layer” indicates a range where effects ofthe present invention can be sufficiently achieved even when a chargecontrol agent is not impregnated on the whole of the substratepolyurethane foam and thus an amount of impregnated charge control agentis small.

In the present invention, the charge control agent is not restricted aslong as the agent is on the negative side or on the positive side in thetriboelectric series with respect to the substrate polyurethane foam,and is substance which is generally used as a charge control agent orelectrification control agent for toner. Here, whether the chargecontrol agent is located on the negative side in the triboelectricseries or is located on the positive side in the triboelectric seriescan be concretely determined by the following method.

(Method for Determining the Location in the Triboelectric Series)

An object material to be measured is left to stand for 4 hours in anatmosphere at a temperature of 23° C., a relative humidity of 55%. Astatic electricity of the object material to be measured is removed bySJ-F300 Static eliminator (manufactured by KEYENCE CORPORATION). Theobject material to be measured is rubbed with polyurethane foam which isused as a substrate (polyurethane foam), and measured with ElectrostaticVoltmeter (manufactured by TREK Japan KK “MODEL 347”). The locations inthe triboelectric series are determined by whether the polyurethane foamand the object material to be measured are positively (plus) charged ornegatively (minus) charged.

Specific examples of charge control agents which are on the negativeside in the triboelectric series with respect to the substratepolyurethane foam which is used in the present invention (hereinafter,referred to as “negatively charged charge control agent”) include (A)boron acid salt, (B) borate ester compound, (C) polyhydroxyalkanoate,(D) metal compound of salicylic acid derivatives, (E) metal compound ofoxynaphthoic acid derivatives, (F) azo-based metal complex compound, (G)metal compound of aromatic oxycarboxylic acid, (H) copolymer in whichmonomers having a sulfonic acid group as copolymerization ingredientsare polymerized, (I) copolymer in which monomers having a carboxyl groupas copolymerization ingredients are polymerized, (J) organometalliccompound in which zirconium or aluminum, zinc, and aromatic compound(s)selected from the group consisting of aromatic diol, aromatic hydroxycarboxylic acid, aromatic monocarboxylic acid and aromaticpolycarboxylic acid are coordinated and/or bonded, (K) complex of boronor aluminum, and benzilic acid derivatives, (L) sulfur-containingresins. These negatively charged charge control agents can be used aloneor two or more thereof can be used in combination. Depending on the kindof toner to be used and the amount of binder, polyvinyl chloride,polyvinyl alcohol and polyvinyl acetate resins used as the binder maysometimes have by itself an effect corresponding to the effect of anegatively charged charge control agent.

As the (A) boron acid salt, for example, sodium salt, potassium salt,ammonium salt or the like is preferred, and particularly potassium saltis more preferred although not restricted thereto.

As the (B) borate ester compound, those which are represented by thefollowing general formula (1):

(in the general formula (1), R¹ and R² represent a hydrogen atom, alkylgroup or aryl group, and may be the same or different; M representsalkali metal or alkaline earth metal; and n is an integer) can bepreferably employed.

In the general formula (1), the alkyl group represented by R¹ and R² isnot restricted, and preferably a C1-18 alkyl group, more preferably, amethyl group, ethyl group, propyl group, butyl group or pentyl group,and particularly preferably a butyl group or pentyl group.

In the general formula (1), examples of the aryl group represented by R¹and R² include a phenyl group, tolyl group, xylyl group, biphenyl group,naphthyl group, anthryl group and phenanthryl group. Among these, aphenyl group is preferred.

Further, in the general formula (1), examples of the alkali metal oralkaline earth metal represented by M include lithium, potassium,calcium and sodium. Lithium and potassium are particularly preferred.

As the (C) polyhydroxyalkanoate, those which are represented by thefollowing general formula (2):

(in the general formula (2), R represents -A¹-(SO₂R³)_(x); R³ representsOH, halogen atom, ONa, OK or OR^(3a); R^(3a) and A¹ represent asubstituted or unsubstituted aliphatic hydrocarbon group, substituted orunsubstituted aromatic group, or substituted or unsubstitutedheterocyclic group; m and x are integers selected from 1 to 8; if aplurality of units exist, R, R³, R^(3a), A¹, m and x representindependently the above meanings for each unit) are preferably employed.

As the (D) metal compound of salicylic acid derivatives, a metalcompound of dialkylsalicylic acid is preferred, and particularly, ametal compound of di-tert-butylsalicylic acid is preferred. As the metalelement, aluminium, gallium, magnesium, calcium, titanium, chromium,zinc, zirconium, hafnium or the like is preferred, and particularly,aluminium compound is preferred.

Examples of the (E) metal compound of oxynaphthoic acid derivativesinclude organometallic compounds composed of oxynaphthoic acidderivatives represented by the following general formula (3):

(in the general formula (3), R⁴ represents a hydrogen atom, linear orbranched alkyl group, alkoxy group, nitro group, amino group, carboxylgroup, aralkyl group, phenyl group, benzyl group or halogen atom; and nrepresents an integer of 0 to 4), and a metal such as aluminium,chromium, cobalt, iron, titanium or zinc.

As the azo metal complex compound, those which are represented by thefollowing general formula (4):

(in the general formula (4), M represents a coordination center metal(chromium, cobalt, nickel, manganese, iron, titanium, aluminium or thelike); Ar represents an aryl group which may have a variety ofsubstituents; X, X¹, Y and Y¹ each represent O, CO, NH or NR⁵ (R⁵ is aC1-4 alkylene group); and A⁺ represents a hydrogen ion, sodium ion,potassium ion, ammonium ion or aliphatic ammonium ion, and these ionsmay be mixed) are preferably employed.

Examples of the (G) aromatic oxycarboxylic acid which constitutes themetal compound of aromatic oxycarboxylic acid include salicylic acid,m-oxybenzoic acid, p-oxycarboxylic acid, gallic acid, mandelic acid andtropic acid. Among these, bivalent or more aromatic carboxylic acids arepreferably employed, and particularly, isophthalic acid, terephthalicacid, trimellitic acid or naphthalene dicarboxylic acid is preferred. Asmetals which form a metal compound with these aromatic carboxylic acids,bivalent or more metal is preferred, and specific examples of the metalsinclude magnesium, calcium, strontium, lead, iron, cobalt, nickel, zinc,copper, zirconium, hafnium, aluminium and chromium.

With respect to the (H) copolymer in which monomers having a sulfonicacid group as copolymerization ingredients are polymerized, as themonomers having a sulfonic acid group, sulfonic acid containingacrylamide monomer is preferred, and examples of the monomers having asulfonic acid group include 2-acrylamidepropanesulfonic acid,2-acrylamide-n-butanesulfonic acid, 2-acrylamide-n-hexanesulfonic acid,2-acrylamide-n-octanesulfonic acid, 2-acrylamide-n-dodecanesulfonicacid, 2-acrylamide-n-tetradecanesulfonic acid,2-acrylamide-2-methylpropanesulfonic acid,2-acrylamide-2-phenylpropanesulfonic acid,2-acrylamide-2,2,4-trimethylpentanesulfonic acid,2-acrylamide-2-methylphenylethanesulfonic acid,2-acrylamide-2-(4-chlorophenyl)propanesulfonic acid,2-acrylamide-2-carboxymethylpropanesulfonic acid,2-acrylamide-2-(2-pyridyl)propanesulfonic acid,2-acrylamide-1-methylpropanesulfonic acid,3-acrylamide-3-methylbutanesulfonic acid,2-methacrylamide-n-decanesulfonic acid and2-methacrylamide-n-tetradecanesulfonic acid. Among these,2-acrylamide-2-methylpropanesulfonic acid is preferably exemplified.

Examples of the copolymerization ingredients include vinyl monomers suchas styrene monomers, olefin monomers, diene monomers, halogenatedvinyls, vinyl esters and (meth)acrylic acid.

As the (I) copolymer in which monomers having a carboxyl group ascopolymerization ingredients are polymerized, as the monomers having acarboxyl group, those which are represented by the following generalformula (5):

(in the general formula (5), R⁶ represents C2-6 alkylene group; R⁷represents a hydrogen atom or methyl group; and n represents an integerof 0 to 10), or those which are represented by the following generalformula (6):

(in the general formula (6), R⁸ represents a hydrogen atom or methylgroup; R⁹ represents a C2-4 alkylene group; R¹⁰ represents an ethylenegroup, vinylene group, 1,2-cyclohexylene group or 1,2-phenylene group)are preferably employed.

As the monomers having a carboxyl group represented by the generalformula (5), for example, (meth)acrylic acid, (meth)acrylic acid dimer,ω-carboxy-polycaprolactone mono(meth)acrylate and the like areexemplified.

As the monomers having a carboxyl group represented by the generalformula (6), for example, succinic acid monohydroxyethyl(meth)acrylate,maleic acid monohydroxyethyl(meth)acrylate, fumaric acidmonohydroxyethyl(meth)acrylate, phthalic acidmonohydroxyethyl(meth)acrylate, 1,2-dicarboxycyclohexanemonohydroxyethyl(meth)acrylate and the like are exemplified.

Further, similarly to the (H) copolymer, examples of thecopolymerization ingredients include vinyl monomers such as styrenemonomers, olefin monomers, diene monomers, halogenated vinyls, vinylesters and (meth)acrylic acid.

The (J) organometallic compound in which zirconium or aluminium, zinc,and aromatic compound(s) selected from the group consisting of aromaticdiol, aromatic hydroxy carboxylic acid, aromatic monocarboxylic acid andaromatic polycarboxylic acid are coordinated and/or bonded is defined asthose in which an aromatic compound as a ligand coordinates to zirconiumor aluminium and zinc to form a metal complex or a metal complex salt.

As the (K) complex of boron or aluminum, and benzilic acid derivatives,those which are represented by the following general formula (7):

(in the general formula (7), M is boron or aluminium; X is lithium,sodium or potassium; R¹¹, R¹², R¹³ and R¹⁴ are each independentlyrepresent a hydrogen atom, C1-4 alkyl group, C1-4 alkoxy group orhalogen atom; a plurality of R¹¹, R¹², R¹³ and R¹⁴ may exist, and if aplurality of R¹¹, R¹², R¹³ and R¹⁴ exist, each of these may be differentor the same; and n represents an integer of 1 to 5) can be preferablyemployed.

As the (L) sulfur resins, a polymer or copolymer which has a sulfonicacid group is preferred, and a polymer or copolymer containing sulfurwhich has a sulfonic acid group-containing acrylamide monomer as aconstituent is particularly preferred.

Examples of sulfonic acid group-containing acrylamide monomers include2-acrylamidepropanesulfonic acid, 2-acrylamide-n-butanesulfonic acid,2-acrylamide-n-hexanesulfonic acid, 2-acrylamide-n-octanesulfonic acid,2-acrylamide-n-dodecanesulfonic acid, 2-acrylamide-n-tetradecanesulfonicacid, 2-acrylamide-2-methylpropanesulfonic acid,2-acrylamide-2-phenylpropanesulfonic acid,2-acrylamide-2,2,4-trimethylpentanesulfonic acid,2-acrylamide-2-methylphenylethanesulfonic acid,2-acrylamide-2-(4-chlorophenyl)propanesulfonic acid,2-acrylamide-2-carboxymethylpropanesulfonic acid,2-acrylamide-2-(2-pyridyl)propanesulfonic acid,2-acrylamide-1-methylpropanesulfonic acid,3-acrylamide-3-methylbutanesulfonic acid,2-methacrylamide-n-decanesulfonic acid,2-methacrylamide-n-tetradecanesulfonic acid. Among these,2-acrylamide-2-methylpropanesulfonic acid is particularly preferred.

As the copolymerization ingredient with the sulfonic acidgroup-containing acrylamide monomer, styrene monomers and acrylicmonomers are preferred, and a combination of styrene and acrylic acidester or a combination of styrene and methacrylic acid ester ispreferably exemplified.

Specific examples of charge control agents which are on the positiveside in the triboelectric series with respect to the substratepolyurethane foam which is used in the present invention (hereinafter,referred to as “positively charged charge control agent”) include (a)copolymer in which (meth)acrylate monomer is polymerized as acopolymerization ingredient, (b) copolymer in which aminogroup-containing monomer is polymerized as a copolymerizationingredient, (c) hydroxyl group-containing amino compound, (d) polymerhaving imidazolium salts as a constituent unit, (e) quaternary ammoniumsalt compound, (f) nigrosine-based compound, and (g)triphenylmethane-based compound. These positively charged charge controlagents can be used alone or two or more thereof can be used incombination. Depending on the kind of toner to be used and the amount ofbinder, polyacrylamide, butadiene resin, epoxy resin, alkyd resin,melamine resin and chloroprene rubber used as the binder may sometimeshave by itself an effect corresponding to the effect of a positivelycharged charge control agent.

As the (a) copolymer in which (meth)acrylate monomer is polymerized as acopolymerization ingredient, those which have as a main ingredient a(meth)acrylate represented by the following general formula (8):

(in the general formula (8), R¹⁵ represents an alkyl group having 4 ormore carbon atoms; R¹⁶ represents a hydrogen atom or methyl group; R¹⁵is preferably an alkyl group having 6 or more carbon atoms, morepreferably an alkyl group having 8 or more carbon atoms, and further,R¹⁵ is preferably an alkyl group having 20 or less carbon atoms; and R¹⁵may be linear or branched and may have a cyclic structure) can bepreferably employed.

Specifically, n-butyl(meth)acrylate, tert-butyl(meth)acrylate,iso-butyl(meth)acrylate, n-amyl (meth)acrylate, n-hexyl(meth)acrylate,cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,n-octyl(meth)acrylate, iso-octyl(meth)acrylate, n-nonyl(meth)acrylate,n-lauryl(meth)acrylate, n-tridecyl(meth)acrylate,n-stearyl(meth)acrylate, isobornyl (meth)acrylate and the like areexemplified. Note that “(meth)acrylate” means methacrylate or acrylate.

The copolymerization ingredient is not particularly restricted, andexamples thereof include vinyl monomers such as (meth)acrylate monomershaving a C1-3 alkyl group, styrene monomers, olefin monomers, dienemonomers, halogenated vinyls, vinyl esters and (meth)acrylic acid. Acopolymer using the after-mentioned (b) amino group-containing monomeris also a preferred mode.

As the (b) copolymer in which amino group-containing monomer ispolymerized as a copolymerization ingredient, those which have as a mainingredient an amino group-containing monomer represented by thefollowing general formula (9):

(in the formula (9), R¹⁷ represents a hydrogen atom or methyl group; R¹⁸represents a bivalent C1-7 organic group; each of R¹⁹ and R²⁰independently is preferably a hydrogen atom or C1-20 organic group, andparticularly a C2-4 organic group; or R¹⁹ and R²⁰ may be chemicallybonded and may have a C4-20 cyclic structure; or R¹⁹ and R²⁰ arechemically bonded and may have a C4-19 cyclic structure which has atleast one selected from a nitrogen atom, oxygen atom, sulfur atom) canbe preferably employed.

Specifically, N,N-dimethylaminoethyl(meth)acrylamide,N,N-diethylaminoethyl(meth)acrylamide,N,N-dimethylaminopropyl(meth)acrylamide,N,N-diethylaminopropyl(meth)acrylamide,p-N,N-dimethylaminophenyl(meth)acrylamide,p-N,N-diethylaminophenyl(meth)acrylamide,p-N,N-dipropylaminophenyl(meth)acrylamide,p-N,N-dibutylaminophenyl(meth)acrylamide,p-N-laurylaminophenyl(meth)acrylamide,p-N-stearylaminophenyl(meth)acrylamide,p-N,N-dimethylaminobenzyl(meth)acrylamide,p-N,N-diethylaminobenzyl(meth)acrylamide,p-N,N-dipropylaminobenzyl(meth)acrylamide,p-N,N-dibutylaminobenzyl(meth)acrylamide,p-N-laurylaminobenzyl(meth)acrylamide,p-N-stearylaminobenzyl(meth)acrylamide and the like are exemplified. Theamino group-containing monomers represented by the general formula (9)can be used alone or two or more thereof can be used in combination.Note that “(meth)acrylamide” means methacrylamide or acrylamide.

As the copolymerization ingredients, the (a) ingredient is preferred.Further, vinyl monomers such as (meth)acrylate monomers having a C1-3alkyl group, styrene monomers, olefin monomers, diene monomers,halogenated vinyls, vinyl esters and (meth)acrylic acid are exemplified.

As the (c) hydroxyl group-containing amino compound, those which arerepresented by the following general formula (10):

or the following general formula (11):

(in the general formulae (10) and (11), R²¹, R²⁴ and R²⁶ are a C1-8alkylene group or an ethyleneoxide group which recurs 1 to 4 times; R²²,R²³, R²⁵, R²⁷, R²⁸ are each a C1-8 alkyl group; and R²² and R²³, R²⁴ toR²⁸ may be the same or different) can be preferably employed.

Specific examples of the hydroxyl group-containing amino compoundsrepresented by the general formulae (10) and (11) includedimethylethanolamine, and as commercially available products “KAOLIZERNo. 25 (trade name)” manufactured by Kao Corporation and “POLYCAT 17(trade name)” manufactured by Sankyo Air Products Co., Ltd.

As the (d) polymer having imidazolium salts as a constituent unit, thosewhich have as a main ingredient an imidazolium salt represented by thefollowing general formula (12):

(in the general formula (12), R²⁹ represents a hydrogen atom or C1-17hydrocarbon group; each of R³⁰ and R³¹ is independently a hydrogen atomor C1-8 hydrocarbon group; or R³⁰ and R³¹ may be connected to form acyclic structure; R³² represents a C1-12 alkylene group which maycontain an ether bond; X⁻ represents an anion; and n represents aninteger of 2 to 100) can be preferably employed.

In the general formula (12), examples of the C1-17 hydrocarbon group inR²⁹ include alkyl groups such as a methyl group, ethyl group, undecylgroup, tridecyl group, pentadecyl group and heptadecyl group; alkenylgroups such as an undecenyl group, tridecenyl group and heptadecenylgroup; alkylphenyl groups such as a pentylphenyl group and hexylphenylgroup; aryl groups such as a phenyl group; and aralkyl groups such as abenzyl group. Among these, a hydrogen atom and C11-17 alkyl group arepreferred, and in particular, an undecyl group, tridecyl group,pentadecyl group and heptadecyl group are preferred.

In the general formula (12), examples of the C1-8 hydrocarbon group inR³⁰ and R³¹ include alkyl groups such as a methyl group, ethyl group,propyl group, butyl group, hexyl group and octyl group; aryl groups suchas a phenyl group; and aralkyl groups such as a benzyl group. As thecyclic structure in which R³⁰ and R³¹ are mutually connected, a benzogroup is exemplified. Among these, a hydrogen atom, methyl group, ethylgroup and benzo group are preferred, and in particular, a hydrogen atomand benzo group are preferred.

In the general formula (12), specific examples of R³² include amethylene group, ethylene group, trimethylene group, tetramethylenegroup, hexamethylene group, octanemethylene group, decamethylene group,dodecamethylene group, and groups such as —CH₂CH₂OCH₂CH₂—,—CH₂CH₂OCH₂OCH₂CH₂— and —CH₂CH₂OCH₂CH₂OCH₂CH₂—. Among these, ethylenegroup, trimethylene group, tetramethylene group, hexamethylene group,—CH₂CH₂OCH₂CH₂—, and —CH₂CH₂OCH₂OCH₂CH₂— are preferred, and inparticular, trimethylene group, tetramethylene group, hexamethylenegroup and —CH₂CH₂OCH₂CH₂— are preferred.

In the general formula (12), examples of X⁻ anion include halogen ion,sulfate ion, nitrate ion, phosphate ion, sulfonic acid ions (e.g.,p-toluene sulfonic acid ion, methylsulfonic acid ion,hydroxynaphtosulfonic acid ion), carboxylic acid ion (e.g., formic acidion, acetic acid ion, propionic acid ion, benzoic acid ion), boric acidion (e.g., boric acid ion, metaboric acid ion, tetrafluoroboric acidion, tetraphenylboric acid ion) and metal oxo-acid ion (e.g., molybdicacid ion, tungstic acid ion). Preferred among these are carboxylic acidion, sulfonic acid ion, boric acid ion and oxo-acid ion.

As the (e) quaternary ammonium salt compound, those which arerepresented by the following general formula (13):

(in the general formula (13), each of R³³, R³⁴, R³⁵ and R³⁶independently represents an alkyl group which may have a substituent,cycloalkyl group which may have a substituent, aralkyl group which mayhave a substituent, aryl group which may have a substituent; and X⁻represents an anion) can be preferably employed.

In the general formula (13), specific examples of the alkyl group inR³³, R³⁴, R³⁵ and R³⁶ include linear or branched C1-8 alkyl groups suchas a methyl group and ethyl group, and examples of the substituentinclude C1-3 alkoxy groups such as a methoxy group and ethoxy group,halogen, a nitro group and a phenyl group.

In the general formula (13), specific examples of the cycloalkyl groupin R³³, R³⁴, R³⁵ and R³⁶ include C3-8 cycloalkyl groups such ascyclopropyl group, cyclopentyl group, cyclohexyl group and cycloheptylgroup, and examples of the substituent include the same groups as thosementioned in the above description about the alkyl groups.

In the general formula (13), specific examples of the aralkyl group inR³³, R³⁴, R³⁵ and R³⁶ include a benzyl group, α,α-dimethylbenzyl group,toluoyl group and phenethyl group, and examples of the substituentinclude the same groups as those mentioned in the above descriptionabout the alkyl groups.

In the general formula (13), specific examples of the aryl group in R³³,R³⁴, R³⁵ and R³⁶ include a phenyl group and naphthyl group, and examplesof the substituent include the same groups as those mentioned in theabove description about the alkyl groups.

In the general formula (13), as the anion represented by X⁻, an organicor inorganic anion is exemplified, and specific examples of the anioninclude a naphthol sulfonic acid anion, an anion of toluene sulfonicacid and a halogen ion.

As the (f) nigrosine-based compound, compounds well-known fornigrosine-based dye can be employed, and, for example, “NIGROSINE BASEEX (trade name)”, “OIL BLACK BS (trade name)”, “OIL BLACK SO (tradename)”, “BONTRON N-01 (trade name)”, “BONTRON N-07 (trade name)”,“BONTRON N-09 (trade name)” and “BONTRON N-11 (trade name)”(manufactured by Orient Chemical Industries Co., Ltd.) are commerciallyavailable.

As the (g) triphenylmethane-based compound, for example, thoserepresented by the following general formula (14):

(in the general formula (14), each of R³⁷ and R³⁹ is independently agroup selected from an amino group, mono- or di-alkylamino group havinga C1-4 alkyl group, mono- or di-ω-hydroxyalkylamino group having a C2-4alkyl group, unsubstituted or N-alkyl-substituted phenylamino group; R³⁸is a hydrogen atom or a group which has been mentioned in R³⁷ and R³⁹;each of R⁴⁰ and R⁴¹ is independently a hydrogen atom, halogen atom,sulfonic acid group, or both R⁴⁰ and R⁴¹ are condensed to form a phenylring; each of R⁴², R⁴³, R⁴⁵ and R⁴⁶ is independently a hydrogen atom,methyl group or ethyl group; R⁴⁴ is a hydrogen atom or halogen atom; andX⁻ is a halogen ion, sulfate, molybdate, phosphomolybdate or boronanion, and among these, preferred are compounds in which R³⁷ and R³⁹ area phenylamino group; R³⁸ is a m-methylphenylamino group; and R⁴⁰ to R⁴⁶are a hydrogen atom) can be preferably employed.

In the present invention, a method of impregnation is not restricted aslong as it is a method in which the surface layer can be impregnatedwith the above-mentioned charge control agent, and is preferably amethod of impregnation with a solution.

In the present invention, substrate polyurethane foam can be providedwith a charging ability according to a conventional method by beingimpregnated with the above-mentioned charge control agent, andparticularly preferably, substrate polyurethane foam is provided with acharging ability by being impregnated with an impregnating solutionwhich contains the above-mentioned charge control agent and binders.

It is preferable that the surface layer is locally impregnated with thecharge control agent. Since charge control agents are insulative, suchaddition of a charge control agent increases the value of resistance ofthe roller. Thus, when a charge control agent is dispersed on the wholeof the polyurethane foam, the value of resistance of the whole rollerincreases and it is difficult to control the value of the resistance ofthe roller in the range 10² to 10⁴Ω which is the target range. In orderto prevent the increase of the value of resistance, carbon conductingagent should be added to the polyurethane foam excessively. In thiscase, when the amount of carbon added increases, the hardness of theroller increases, as well as the amount of carbon which can be detachedfrom the polyurethane foam when the polyurethane foam is in contact witha developing roller during a long-term usage becomes significant, and apoor image generation is caused, which is problematic and not preferred.Therefore, from the viewpoint of attaining the above-mentioned value ofresistance of the roller and a stable image property during a long-termusage, it is preferred that a charge control agent is locally disposedon the surface layer of the polyurethane foam.

In the present invention, the below-described electrically conductivematerial may be added to the impregnating solution. As the electricallyconductive material, carbonaceous particles such as carbon black andgraphite; powder of metal such as silver and nickel; electricallyconductive metal oxide by itself such as tin oxide, titanium oxide orzinc oxide; or those which have an insulating particle made of, forexample, barium sulfate as a core body covered with the above-mentionedelectrically conductive metal oxide by using a wet process; electricallyconductive metal carbide, electrically conductive metal nitride,electrically conductive metal boride or the like is employed alone, ortwo or more of those are employed in combination. From the viewpoint ofcost, carbon black is preferred, and on the other hand, from theviewpoint of controllability of electrical conductivity, electricallyconductive metal oxide is preferred.

As the above-mentioned binders, acrylic resins such as acrylate resins,polyacrylate resins, acrylate-styrene copolymer resins, acrylate-vinylacetate copolymer resins; polyvinyl alcohols, polyacrylamides, polyvinylchloride resins, urethane resins, vinyl acetate resins, butadieneresins, epoxy resins, alkyd resins, melamine resins, and chloroprenerubbers or the like may be exemplified. Particularly preferred areacrylate resins, urethane resins and chloroprene rubbers such as tradename: SE BINDER manufactured by ENEX CO., LTD., and trade name: TOCRYLBC-X6131, TOCRYL 5744 and TOCRYL X4402 manufactured by TOYO INK MFG.CO., LTD. These binders may be used alone or in combination as a mixtureof two or more thereof. Although the charge control agent by itselfcannot bind rigidly to the cell wall of polyurethane foam, the chargecontrol agent adheres rigidly to the cell wall of polyurethane foam byadding the binder to form as the surface layer a stable charge controlagent layer in cells of the polyurethane foam.

In the present invention, the compounding ratio of the charge controlagent and the binder is preferably 10 to 110 parts by mass, particularly30 to 50 parts by mass of solid content of the charge control agent withrespect to 100 parts by mass of solid content of the binder. If thecharge control agent is larger than 110 parts by mass, adhesion topolyurethane foam tends to be insufficient. On the other hand, if thecharge control agent is smaller than 10 parts by mass, the surfaceresistance of the toner-providing roller tends to be unstable.

To the impregnating solution which contains the charge control agent andthe binder, a proper amount of water and an organic solvent such astoluene or ethyl acetate may be added. Such solvents are preferablyadded such that a viscosity of the impregnating solvent is about 5 to300 cps (25° C.). Setting the viscosity in this range makes an adhesionoperation by impregnation more readily.

In the present invention, to the impregnating solution, other additivesthan those mentioned above, such as mineral oil-based antifoamingagents, silicone-based antifoaming agents, surfactants and chargecontrol agents may be added as required. Such additives are preferablyadded at an amount of about 0.001 to 10 parts by mass, particularly atan amount of 0.001 to 0.1 part by mass with respect to 100 parts by massof the impregnating solution.

Examples of the mineral oil-based antifoaming agents includeself-emulsifying type silicone-based antifoaming agents under the tradenames of: KS-508 and KS-537, oil type silicone-based antifoaming agentunder the trade name of: KF-96, and oil compound type silicone-basedantifoaming agent under the trade name of: KF-66 manufactured byShin-Etsu Chemical Co., Ltd.

A toner-conveying roller of the present invention supports theabove-mentioned charge-controlled polyurethane foam on the periphery ofthe axis of the roller, and is suitably applied to an image formingapparatus. FIG. 1 is a cross-sectional view of the toner-conveyingroller of a preferred embodiment of the present invention in the widthdirection. The toner-conveying roller of the present invention shown inthe figure supports charge-controlled polyurethane foam 3 on theperiphery of an axis 1 of the roller via an adhesion layer 2. By this,the influence of electrification by friction between toner on thesurface layer of a toner-conveying roller and a developing roller can besufficiently prevented and a good image can be obtained with a low cost.

The toner-conveying roller of the present invention is preferably aroller wherein the charge control agent is on the negative side in thetriboelectric series with respect to the polyurethane foam, and whereinthe roller is for positively charged toner; or is preferably a rollerwherein the charge control agent is on the positive side in thetriboelectric series with respect to polyurethane foam, and wherein theroller is for negatively charged toner.

The mechanism by which toner 20 is conveyed from a toner-conveyingroller 13 to a developing roller 12 is as shown in FIG. 2. Firstly, tothe positively (or negatively) charged toner 20, the surface layer ofthe toner-conveying roller 13 is negatively (or positively) charged byfriction between the toner 20 and the developing roller 12. In thecharged toner-conveying roller 13, by releasing charge via an axis 1comprised of a cored bar or the like, the charge amount (the amount ofelectric charge) of the surface layer of the toner-conveying roller 13is controlled. In this case, the less the charge amount of the surfacelayer of the toner-conveying roller 13 is, the harder the toner 20 is tobe absorbed to the surface layer of the toner-conveying roller 13, andas a result, the amount of toner to be conveyed can be increased.

Further, an impregnation amount of the charge control agent (negativelycharged charge control agent or positively charged charge control agent)in the charge-controlled polyurethane foam of the toner-conveying rolleris preferably in the range of 0.1 to 50 parts by mass with respect to100 parts by mass of the polyurethane foam. If the impregnation amountof the charge control agent is not smaller than 0.1 part by mass, theeffect of the charge control agent can be further obtained. On the otherhand, if the impregnation amount of the charge control agent is notlarger than 50 parts by mass, the effect of preventing detachment of thecharge control agent from the polyurethane foam can be obtained. Thecontent of charge control agent is further preferably 1 to 5 parts bymass with respect to 100 parts by mass of the polyurethane foam. Bythis, the above-mentioned effect can be further obtained.

A roller of the present invention is not particularly restricted exceptthat the surface layer of the substrate polyurethane foam is impregnatedwith charge control agent which is on the negative side or on thepositive side in the triboelectric series with respect to the substratepolyurethane foam. A detail structure of the roller, materials of theroller, or the like can be appropriately determined as required.

In the present invention, polyurethane foam which is used as a substratecan be manufactured by a method described in Japanese Patent No.3480028, in which method a compound which has two or more activehydrogens and a compound which has two or more isocyanate groups arestirred and mixed with additives such as catalysts, foaming agents andfoam stabilizers to be foamed and hardened, or can be manufactured by amethod using water as a foaming agent, in which method, for example,foam forming materials including a prepolymer made by reacting anisocyanate ingredient and a polyol ingredient in advance,water-dispersed carbon, a catalyst for the urethane reaction and thelike are foamed in a prescribed form and thereafter heated to behardened, a prepolymer method, a one-shot method, a partial prepolymermethod or the like. For example, the polyurethane foam can bemanufactured by mixing a polyether polyol including a mixture ofhomogeneous diols including two kinds of homogeneous diols which have anaverage molecular weight difference therebetween of 800 to 3600 at notless than 50% by mass in total with respect to polyol ingredient,isocyanate, water, catalyst and foaming agent, being foamed and beingleft to stand.

As used herein, “homogeneous diol” generally means one diol or two ormore kinds of diols having an average molecular weight differencetherebetween of 400 or less. Also, an “average molecular weightdifference” means a difference between the respective average molecularweights of object diols. If there is a lot of combinations of thedifference, an “average molecular weight difference” particularly meansthe largest difference.

As the polyol ingredient used for manufacturing the prepolymer, forexample, polyether polyols made by addition polymerization of ethyleneoxide and propylene oxide, polytetramethylene ether glycol, polyestherpolyol made by condensing an acid ingredient and a glycol ingredient,polyester polyol made by ring-open polymerization of caprolactone,polycarbonate diols or the like can be used.

In the present invention, examples of a polyether polyol used formanufacturing the substrate polyurethane foam include (1) a polyetherpolyol of such a type that, for example, propylene oxide alone is addedto diethylene glycol, (2) a polyether polyol of such a type that, forexample, propylene oxide and ethylene oxide are added in block orrandomly to diethylene glycol, and (3) a polyether polyol of such a typethat, for example, acrylonitrile or styrene is grafted to the above (1)or (2), but not restricted thereto, and in order to achieve more effect,the polyether polyol of type (1) is preferred.

Examples of initiator used for manufacturing the polyether polyolinclude polyalcohols, polyphenols, mono- or poly-amine, and others.Polyalcohols and polyphenols are preferred, and polyalcohols are morepreferred. Examples thereof include ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol.Among these, diethylene glycol is particularly preferred.

Examples of the polyether polyol ingredients may include polyolingredients other than diols. Examples of such polyol ingredientsinclude a trifunctional polyol usually used for manufacturing substratepolyurethane foam such as a polyol in which an alkylene oxide such as apropylene oxide is added to glycerin base, or a polyol made by addingtwo kinds of alkylene oxides such as propylene oxide and ethylene oxiderandomly or in block. Examples of a polyfunctional polyol include apolyether polyol in which the same substances as above are added tosaccharose base.

As the polyether polyol which is made by addition polymerization ofethylene oxide and propylene oxide, a polyether polyol which is made byaddition polymerization of ethylene oxide and propylene oxide by usingas a starting material, for example, water, propylene glycol, ethyleneglycol, glycerin, trimethylolpropane, hexane triol, triethanol amine,diglycerine, pentaerythritol, ethylene diamine, methyl glucoside,aromatic diamine, sorbitol, sucrose or phosphoric acid is exemplified,and a polyether polyol which is made by using as a starting materialwater, propylene glycol, ethylene glycol, glycerin, trimethylolpropaneor hexane triol is particularly preferred. With respect to thepercentage of ethylene oxide and propylene oxide to be added and themicrostructures of the polyether polyol, the percentage of ethyleneoxide is preferably 2 to 95% by mass, and more preferably 5 to 90% bymass; and a polyether polyol which has etheylene oxide at a terminalthereof is preferred. The sequence of ethylene oxide and propylene oxidein the molecular chain is preferably random.

With respect to the molecular weight of the polyether polyol, whenwater, propylene glycol or ethylene glycol is used as a startingmaterial, the polyether polyol is bifunctional, and the molecular weightis preferably in the range of 300 to 6000 in terms of weight-averagemolecular weight, and more preferably in the range of 3000 to 5000. Whenglycerin, trimethylolpropane or hexane triol is used as a startingmaterial, the polyether polyol is trifunctional, and the molecularweight is preferably in the range of 900 to 9000 in terms ofweight-average molecular weight, and more preferably in the range of4000 to 8000. Further, bifunctional polyol and trifunctional polyol maybe used by blending them appropriately.

The polytetramethylene ether glycol may be obtained, for example, bycationic polymerization of tetrahydrofuran. A polytetramethylene etherglycol having a weight-average molecular weight in the range of 400 to4000, and particularly in the range of 650 to 3000 is preferablyemployed. Polytetramethylene ether glycols having different molecularweights are preferably blended. Further, a polytetramethylene etherglycol obtained by copolymerization of alkylene oxide(s) such asethylene oxide and/or propylene-oxide may also be employed.

Further, the polytetramethylene ether glycol and the polyether polyolmade by addition polymerization of ethylene oxide and propylene oxideare preferably blended to be used. In this case, the blend ratio thereofis suitably in the range of 95:5 to 20:80 in terms of mass ratio, andparticularly, in the range of 90:10 to 50:50.

The above-mentioned polyol ingredient may be used in combination withpolyols such as a polymer polyol which is an acrilonitrile modifiedpolyol, a polyol to which melamine is added, diols such as butanediol,trimethylol propane or derivatives thereof.

As the polyisocyanate ingredient used in the present invention, aromaticisocyanate or derivatives thereof, aliphatic isocyanate or derivativesthereof, or cycloaliphatic isocyanate or derivatives thereof is used.Among these, aromatic isocyanate or derivatives thereof is preferred,and particularly, tolylene diisocyanate (TDI) or derivatives thereof,diphenylmethane diisocyanate (MDI) or derivatives, thereof,polymethylene polyphenyl isocyanate or derivatives thereof is preferablyused, and used alone or used by mixing.

As the tolylene diisocyanate or derivatives thereof, crude tolylenediisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, amixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, ureamodified product thereof, biuret modified product thereof, carbodiimidemodified product thereof or urethane modified product modified by, forexample, polyol is used. As the diphenylmethane diisocyanate orderivatives thereof, for example, a diphenylmethane diisocyanate orderivatives thereof obtained by phosgenating diamino diphenyl methane orderivatives thereof is used. Examples of the derivatives of diaminodiphenyl methane include a polynuclear one, and pure diphenyl methanediisocyanate obtained by diamino diphenyl methane, polymericdiphenylmethane diisocyanate obtained by polynucleardiaminodiphenylmethane, or the like may be used. With respect to thenumber of functionalities of polymeric diphenylmethane diisocyanate, amixture of pure diphenylmethane diisocyanate and polymericdiphenylmethane diisocyanates having a variety of numbers offunctionalities is usually used, and those having an average number offunctionalities of preferably 2.05 to 4.00, and more preferably 2.50 to3.50 are used. Derivatives obtained by modifying these diphenylmethanediisocyanates or derivatives thereof such as urethane modified productmodified by, for example, polyol, a dimer made by uretdione formation,isocyanurate modified product, carbodiimide/uretonimine modifiedproduct, allophanate modified product, urea modified product, biuretmodified product may also be used. Also, several kinds ofdiphenylmethane diisocyanates or derivatives thereof may be blended tobe used.

In the present invention, as a prepolymerization method, a method inwhich polyol and isocyanate are put into an appropriate container,stirred sufficiently and kept warm at a temperature of 30 to 90° C.,more preferably, 40 to 70° C., for 6 to 240 hours, more preferably for24 to 72 hours is exemplified. In this case, the quantity percentages ofpolyol and isocyanate are preferably adjusted such that the content ofisocyanate of the obtained prepolymer is 4 to 30% by mass, and morepreferably 6 to 15% by mass. If the content of isocyanate is smallerthan 4% by mass, stability of the prepolymer is impaired, the prepolymerhardens during storage, and therefore, it may become unusable. If thecontent of isocyanate is larger than 30% by mass, the content ofisocyanate which is not prepolymerized increases, and thispolyisocyanate is hardened with polyol ingredient which is used in thesubsequent polyurethane hardening reaction by a similar reactionmechanism to a one-shot manufacturing method which does not undergo aprepolymerization reaction, and thereby deteriorating the effect ofusing the prepolymer method.

To the substrate polyurethane foam, in addition to the above-mentionedpolyol ingredient and isocyanate ingredient, an electrically conductivematerial such as carbon black, a crosslinking agent, a surfactant, acatalyst, a foam stabilizer or the like may be added, if desired, andwhereby a layer structure as desired can be attained. Fire retardants,fillers, antioxidants, ultraviolet absorber or the like can also besuitably used.

Examples of ion conductive materials include ammonium salts such asperchlorate, chlorate, hydrochloride, bromate, iodate, fluoroboric acidsalt, sulphate, alkyl sulfate, carboxylate, sulfonate or the like oftetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (e.g.,lauryltrimethylammonium), hexadecyltrimethylammonium,octadecyltrimethylammonium (e.g., stearyltrimethylammonium),benzyltrimethylammonium, degenerated fatty acid dimethylethylammonium orthe like, perchlorate, chlorate, hydrochloride, bromate, iodate,fluoroboric acid salt, trifluoro methylsulfuric acid salt, sulfonate orthe like of alkali metal and alkaline earth metal such as lithium,sodium, potassium, calcium, magnesium or the like.

Examples of carbon conductive materials include gas blacks such as denkablack, ketjchen black, acetylene black, oil furnace black, thermalblack, channel black, lamp black including ink black. The substratepolyurethane foam according to the present invention is preferably thosewhich is impregnated with such a carbon conductive material or those inwhich carbon conductive material is added.

Further, examples of electronically conductive materials includeelectrically conductive metal oxides such as tin oxide, titanium oxideand zinc oxide; and metals such as nickel, copper, silver and germanium.These electrically conductive materials may be used alone or may be usedby mixing two or more thereof. The amount to be added is not restricted,and can be selected appropriately as desired. The amount to be added isusually 0.1 to 40 parts by mass, preferably 0.3 to 20 parts by mass withrespect to 100 parts by mass of the total amount of polyol andisocyanate.

It is preferred to add, in the substrate polyurethane foam, a siliconefoam stabilizer or a variety of surfactants in order to stabilize cellsof foam material. As the silicone foam stabilizer,dimethylpolysiloxane-polyoxyalkylene copolymer or the like is suitablyemployed, and those which have dimethylpolysiloxane portion having amolecular weight of 350 to 15000 and polyoxyalkylene portion having amolecular weight of 200 to 4000 are particularly preferred. Themolecular structure of polyoxyalkylene portion is preferably an additionpolymer of ethyleneoxide or an addition polymer of both ethyleneoxideand propylene oxide, and also, the ends of the molecular are preferablyethyleneoxide. Examples of the surfactants include ionic surfactantssuch as cationic surfactant, anionic surfactant and ampholyticsurfactant, and nonionic surfactants such as a variety of polyethers anda variety of polyesters. These may be used alone or two or more thereofmay be used in combination. The amounts of silicone foam stabilizer anda variety of surfactants to be added are preferably 0.1 to 10 parts bymass, and more preferably 0.5 to 5 parts by mass with respect to 100parts by mass of the total amount of polyol ingredient and isocyanateingredient.

In the present invention, the kind and the amount of the compound usedas a foaming agent are not particularly restricted, and known compoundsmay be employed. As the foaming agent, for example, methylene chloride,Freon 123 and Freon 14lb are employed.

Examples of the catalyst which is used for the hardening reaction of thesubstrate polyurethane foam include monoamines such as triethylamine,dimethylcyclohexylamine; diamines such as tetramethylethylenediamine,tetramethylpropanediamine, tetramethylhexanediamine; triamines such aspentamethyldiethylenetriamine, pentamethyldipropylenetriamine,tetramethylguanidine; cyclic amines such as triethylenediamine,dimethylpiperazine, methylethylpiperazine, methylmorpholine,dimethylaminoethylmorpholine, dimethylimidazole; alcohol amines such asdimethylaminoethanol, dimethylaminoethoxyethanol,trimethylaminoethylethanolamine, methylhydroxyethylpiperazine,hydroxyethylmorpholine; etheramines such asbis(dimethylaminoethyl)ether, ethylene glycol bis(dimethyl)aminopropylether; organometallic compound such as stannous octate, dibutyltindiacetate, dibutyltin dilaurate, dibutyltin mercaptide, dibutyltinthiocarboxylate, dibutyltin dimaleate, dioctyltin mercaptide, dioctyltinthiocarboxylate, phenyl mercuric propionate, lead octenoate. Thesecatalysts may be used alone, or two or more of these may be used incombination.

In the present invention, the air permeability of the charge-controlledpolyurethane foam is preferably 100 to 700 cm³/cm²/sec, and inparticular, the air permeability of the charge-controlled polyurethanefoam is more preferably about 150 to 400 cm³/cm²/sec. If the airpermeability is larger than 700 cm³/cm²/sec, a toner-efficiency maydecrease due to an excessive toner density. On the other hand, if theair permeability is smaller than 100 cm³/cm²/sec, the substratepolyurethane foam is less likely to be impregnated with an impregnatingsolution during the impregnation process, and therefore, the amounts ofa charge control agent and binder to be attached may be less likely tobe constant. This may lead to a decrease in productivity. Note that theabove-mentioned air permeability was measured in accordance with JIS K6400 standard.

In the present invention, the number of cells in the charge-controlledpolyurethane foam is preferably 20 to 80/inch (25.4 mm), and morepreferably 30 to 60/inch. If the number of cells in thecharge-controlled polyurethane foam is smaller than 20/inch, a space towhich toner attaches decreases, and thus the development is likely to beaffected. On the other hand, if the number of cells in thecharge-controlled polyurethane foam is larger than 80/inch, thesubstrate polyurethane foam is less likely to be impregnated with animpregnating solution during the impregnation process, and therefore,the amounts of the charge control agent and binder to be attached may beless likely to be constant. Moreover, impregnation speed may become slowand the cost may rise.

Further, the average cell diameter of the charge-controlled polyurethanefoam is preferably 50 to 1000 μm, and more preferably about 100 to 400μm. If the average cell diameter is larger than 1000 μm, atoner-efficiency may decrease due to an excessive toner density. On theother hand, if the average cell diameter is smaller than 50 μm, thesubstrate polyurethane foam is less likely to be impregnated with animpregnating solution during the impregnation process, and therefore,the amounts of the charge control agent and binder to be attached may beless likely to be constant.

In the present invention, the density of the charge-controlledpolyurethane foam is preferably 10 to 100 kg/m³, and more preferablyabout 10 to 50 kg/m³. If the density is larger than 100 kg/m³, the costmay rise. On the other hand, if the density is smaller than 10 kg/m³, acompression residual strain is likely to be degraded, and a followingresponse withers, which may cause blur.

The hardness of the charge-controlled polyurethane foam is preferably anASKER F hardness of 30 to 90°. If the hardness is larger than 90°, tonermay deteriorate, and if the hardness is smaller than 30°, a poorpolishing is likely to be caused, which is not desirable.

An axis 1 used for a roller of the present invention is not restricted,and any material can be used. For example, steels such as sulfurfree-cutting steel plated with nickel, zinc or the like, a cored barcomposed of a metal solid body made of iron, stainless steel, aluminum,or the like, or a metal shaft such as a hollow metal cylindrical bodycan be employed. In the present invention, it is preferred that thediameter of the axis 1 is smaller than 6 mm, for example, 5.0 mm, andthe thickness of charge-controlled polyurethane foam 3 is smaller than4.5 mm, for example, 4.0 mm. This can make the roller light, and at thesame time, the thinned charge-controlled polyurethane foam 3 increasesthe macroscopic elastic modulus of the polyurethane foam to improve thetoner sweeping ability. The volume decrease due to the thinnedcharge-controlled polyurethane foam 3 reduces the toner amount which thecharge-controlled polyurethane foam 3 contains during an enduranceprinting, and thus the toner-efficiency can be controlled.

Further, in the roller of the present invention, as illustrated, it ispreferred that an adhesion layer 2 be provided between the axis 1 andthe charge-controlled polyurethane foam 3. As an adhesive used for theadhesive layer 2, a hot-melt polymer adhesive which has, as a mainingredient, an adipate-based polyurethane resin having a melting pointof 120° C. or higher, and particularly 130° C. or higher and 200° C. orlower can be suitably employed.

As the characteristics of the adhesive, any forms such as films andpellets may be employed. The thickness of the adhesion layer 2 ispreferably 20 to 300 μm. In a case when the thickness is too small, apoor adhesion occurs, and in a case when the thickness is too large, apreferable roller resistance cannot be obtained. Neither of the cases ispreferred. It is preferred that the melting temperature of the adhesiveat the time of adhesion be 100° C. or higher, and particularly 130° C.or higher and 200° C. or lower, and be a temperature lower than themelting point of the adhesive. By this, the adhesion layer 2 becomes ina semi-molten state, and thus it becomes easy to controlvoltage-dependencies such as to set a roller resistance from 10⁶ to 10⁸Ωwhen a voltage of 5 V is applied and to set a roller resistance from 10²to 10⁴Ω when a voltage of 100 V is applied, which can increase theinitial density of an endurance printing.

A toner-conveying roller of the present invention can be manufactured bysupporting the periphery of the axis 1 with the charge-controlledpolyurethane foam 3 via an adhesive as required, and then heat-bindingthe axis 1 and the charge-controlled polyurethane foam 3 at a prescribedtemperature.

In concrete, the charge-controlled polyurethane foam 3 is molded in anyshapes such as in a slab form. In the present invention, in the courseof molding the charge-controlled polyurethane foam 3, a method canpreferably be employed in which, by using a low-pressure foamingmachine, a prepolymer and a mixture of the other ingredients are mixedby a mixing rotor at a mechanical head portion, and the resultingmixture is poured into a mold having a temperature of 40 to 80° C. to behardened by heating. The charge-controlled polyurethane foam 3 which canbe molded by this method is a foam which has a lower hardness than thoseobtained by mechanical gas filling such as an ASKER F hardness of 30 to90°.

A film of adhesive is formed on the periphery of the axis 1 by winding afilm adhesive thereon, or by melting pellet adhesive to be appliedthereto. Then, a hole is formed on the charge-controlled polyurethanefoam 3, and the axis 1 with adhesive is inserted into the hole. Then,the resultant is heated at a prescribed temperature to integrate theaxis 1 and the charge-controlled polyurethane foam 3 via the adhesionlayer 2. The surface of the charge-controlled polyurethane foam 3 isground into a desired cylindrical shape, and further, the ends of thecharge-controlled polyurethane foam 3 are cut to make a prescribedshape, whereby a toner-conveying roller of the present invention can beobtained.

EXAMPLES

The present invention will be described more concretely by way ofExamples and Comparative Examples. However, the present invention is notlimited thereto without departing from the scope of the invention.

<Materials>

In the following, materials used in Examples and the Comparative Exampleare shown.

polyurethane foam A manufactured by BRIDGESTONE CORPORATION (withoutmembrane exclusion treatment) density  29 kg/m³ air permeability 196cm³/cm²/sec hardness  10 kgf average cell diameter 280 μm binder a “SEBINDER” urethane resin dispersant in water, solid content 50%;manufactured by ENEX CO., LTD. binder b “TOCRYL BC-X6131” urethane resindispersant in water, solid content 50%; manufactured by TOYO INK MFG.CO., LTD. charge control agent copolymer of acrylate monomer“BS-050301-1” manufactured by ENEX CO., LTD. antifoaming agent “KS-502”manufactured by Shin-Etsu Chemical Co., Ltd.

Example 1

In accordance with a recipe (unit: g) shown in Table 1, the above-listedbinder a, charge control agent, antifoaming agent were mixed to preparean impregnating solution. In a bath filled with the impregnatingsolution, a block (16 mm×1000 mm×2000 mm) polyurethane foam A withoutmembrane exclusion treatment was immersed and compressed between tworolls, and then released to be impregnated with the impregnatingsolution. The polyurethane foam A was introduced out of the bath and theresidual impregnating solution was squeezed to be removed therefrom vianip rolls, then the polyurethane foam A was dried by heating in a hotblast stove at a temperature of 110° C. for 10 minutes, wherebycharge-controlled polyurethane foam was obtained. The amount of theimpregnating solution attached to the charge-controlled polyurethanefoam was 8 g/L in terms of dry mass.

The amount of impregnating solution attached can be adjusted byadjusting the pressure of the compression after taking the blockpolyurethane foam out of the impregnating solution or by changing theconcentrations of the charge control agent and binder in theimpregnating solution.

A hole for insertion of a shaft was punched out on the thus obtainedcharge-controlled block polyurethane foam impregnated with the chargecontrol agent and binder, and a shaft (diameter: 6.0 mm, length: 250 mm)to which an adhesive was applied was inserted into the hole. Then, theblock polyurethane foam was ground into an elastomeric foam having auniform thickness, whereby a toner-conveying roller of the presentinvention was made.

Example 2

As a binder for an impregnating solution, binder b was used; theinterval of nip rolls was adjusted; and the amount of the impregnatingsolution attached (dry mass) was set at 11 g/L. Toner-conveying rollerwas made in the same manner as in Example 1 except for the above.

Comparative Example 1

As a binder for an impregnating solution, binder a was used; theinterval of nip rolls was adjusted; and the amount of the impregnatingsolution attached (dry mass) was set at 3.5 g/L. Toner-conveying rollerwas made in the same manner as in Example 1 except for the above.

<Evaluation>

The physical properties of the toner-conveying rollers obtained inExamples 1 and 2 and Comparative Example 1 were evaluated as describedbelow. The results are also shown in Table 1.

(1) Average Cell Diameter (μm)

The surface of the polyurethane foam was imaged by a microscope, celldiameters on the surface of the polyurethane foam were measured todetermine the average of the cell diameters.

(2) Asker F Hardness (°)

Polyurethane foam was placed on a rigid plate and measured using anAsker Durometer type F manufactured by KOBUNSHI KEIKI CO., LTD. Thehardness 10 seconds after the time when the durometer was placed stillwas measured.

(3) Air Permeability (cm³/cm²/sec)

The air permeability was measured in accordance with JIS K 6400.

(4) The Number of Cells (/inch)

The number of the cells was measured in accordance with JIS K 6400.

(5) Skeletal Shape

The surface of the polyurethane foam was photographed at a magnificationof 100, and judged whether the skeletal shape had an edge or not (theurethane skeleton which did not have a radius corner was defined as“having an edge”).

(6) Evaluation of Image

The toner-conveying rollers obtained in Examples 1 and 2, and theComparative Example 1 were set in commercially available printers, andprinting processes were conducted under the below-mentioned conditionsto evaluate the printing performances.

20000 sheets of A4-size papers are printed in a 4% printing pattern. Inthe course that 20000 sheets of A4-size papers are printed, 3consecutive sheets are printed in a black 100% pattern for every 1000sheets. 3 consecutive sheets are printed in a black 100% pattern for 20times in total. For each 100% pattern printing, an evaluation wasconducted in three grades as described below. The average grade for 20evaluations is calculated (image average evaluation). As the toner,negatively charged toner was used.

(Evaluation Criteria)

A case when blur is occurred on the first or second sheet of the threesheets represents x.A case when blur is occurred on the third sheet of the three sheetsrepresents Δ.A case when no blur is occurred on the three sheets represents ◯.

After printing 20000 sheets of A4-size, 3 consecutive sheets wereprinted in a black 100% pattern. An evaluation was conducted in threegrades as described below to evaluate an image durability (imagedurability evaluation).

(Evaluation Criteria)

A case when blur is occurred on the first or second sheet of the threesheets represents x.A case when blur is occurred on the third sheet of the three sheetsrepresents Δ.A case when no blur is occurred on the three sheets represents ◯.

TABLE 1 Comparative Example 1 Example 2 Example 1 Amount of Binder a 100— 100 impregnating Binder b — 100 — solution Charge control agent 300300 — Antifoaming agent 0.3 0.3 0.3 Amount of impregnating solutionattached 8 11 3.5 (dry mass, % by mass) Membrane exclusion treatment ofpolyurethane foam Not applied Not applied Not applied Evaluation Averagecell diameter (μm) 300 310 305 Asker F hardness (°) after immersion* 6985 60 Air permeability after immersion 200 210 195 (cm³/cm²/sec) Numberof cells (/inch) 38 38 38 Skeletal shape (with or without edge) withedge with edge with edge Image average evaluation ◯ ◯ X Image enduranceevaluation ◯ ◯ X *The thickness was set to 10 mm.

DESCRIPTION OF SYMBOLS

-   1 axis-   2 adhesion layer-   3 charge-controlled polyurethane foam-   11 image forming body-   12 developing roller-   13 toner-conveying roller-   14 toner storage unit-   15 transfer roller-   16 charge unit-   17 exposure unit-   18 blade-   20 toner

1. Charge-controlled polyurethane foam, wherein the surface layer of thepolyurethane foam is impregnated with a charge control agent which is onthe negative side or on the positive side in the triboelectric serieswith respect to substrate polyurethane foam.
 2. The charge-controlledpolyurethane foam according to claim 1, wherein said substratepolyurethane foam is substrate polyurethane foam impregnated with acarbon conductive material or substrate polyurethane foam in which acarbon conductive material is added.
 3. The charge-controlledpolyurethane foam according to claim 1, wherein said charge controlagent is negatively charged charge control agent and said negativelycharged charge control agent is one or more selected from the groupconsisting of (A) boron acid salt, (B) borate ester compound, (C)polyhydroxyalkanoate, (D) metal compound of salicylic acid derivatives,(E) metal compound of oxynaphthoic acid derivatives, (F) azo-based metalcomplex compound, (G) metal compound of aromatic oxycarboxylic acid, (H)copolymer in which monomers having a sulfonic acid group ascopolymerization ingredients are polymerized, (I) copolymer in whichmonomers having a carboxyl group as copolymerization ingredients arepolymerized, (J) organometallic compound in which zirconium or aluminum,zinc, and aromatic compound(s) selected from the group consisting ofaromatic diol, aromatic hydroxy carboxylic acid, aromatic monocarboxylicacid and aromatic polycarboxylic acid are coordinated and/or bonded, (K)complex of boron or aluminum, and benzilic acid derivatives, (L)sulfur-containing resins.
 4. The charge-controlled polyurethane foamaccording to claim 1, wherein said charge control agent is a positivelycharged charge control agent and said positively charged charge controlagent is one or more selected from the group consisting of (a) copolymerin which (meth)acrylate monomer is polymerized as a copolymerizationingredient, (b) copolymer in which amino group-containing monomer ispolymerized as a copolymerization ingredient, (c) hydroxylgroup-containing amino compound, (d) polymer having imidazolium salts asa constituent unit, (e) quaternary ammonium salt compound, (f)nigrosine-based compound, and (g) triphenylmethane-based compound.
 5. Atoner-conveying roller which comprises supporting the charge-controlledpolyurethane foam according to claim 1 on the periphery of the axis ofthe roller.
 6. A toner-conveying roller which comprises supporting thecharge-controlled polyurethane foam according to claim 2 on theperiphery of the axis of the roller.
 7. The toner-conveying rolleraccording to claim 5, wherein said charge control agent is on thenegative side in the triboelectric series with respect to said substratepolyurethane foam, and wherein the roller is for positively chargedtoner.
 8. The toner-conveying roller according to claim 5, wherein saidcharge control agent is on the positive side in the triboelectric serieswith respect to said substrate polyurethane foam, and wherein the rolleris for negatively charged toner.